earth science

Ophirite

Ophirite is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ophirite rather than just read about it. In short: Ophirite is a tungstate mineral first discovered in the Ophir Hill Consolidated mine at Ophir district, Oquirrh Mountains, Tooele County, Utah, United States of America. It was found underground near a calcite cave in one veinlet, six centimeters wide by one meter long, surrounded by different sulfides.

Key takeaways

Ophirite belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ophirite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ophirite from memory before moving on to harder problems.

Reference excerpt

Ophirite is a tungstate mineral first discovered in the Ophir Hill Consolidated mine at Ophir district, Oquirrh Mountains, Tooele County, Utah, United States of America. It was found underground near a calcite cave in one veinlet, six centimeters wide by one meter long, surrounded by different sulfides. Before the closing of the mine in 1972, it was dominated by sulfide minerals, and the Ophir district was known for being a source of zinc, copper, silver, and lead ores. The crystals are formed as tablets. It is the first known mineral to contain a heteropolyanion, a lacunary defect derivative of the Keggin anion. The chemical formula of ophirite is Ca2Mg4[Zn2Mn3+2(H2O)2(Fe3+W9O34)2] · 46•H2O. The mineral has been approved by the Commission on New Minerals and Mineral Names, IMA, to be named ophirite for its type locality, the Ophir Consolidated mine.

Occurrence Ophirite is found in association with scheelite and pyrite. The production of the mineral is thought to be from oxidative alteration of sulfides: a reaction between dolomite and scheelite with oxidizing and late acidic hydrothermal solutions that are in the presence of calcium-rich and pyrite hornfels. It occurs in one veinlet, which is surrounded by sphalerite, galena, bournonite, unidentified sulfide minerals, foci of apatite, and sericite-containing pyrite, and is typically interface between scheelite and dolomite. Also present in the vein are crystals of sulfur and fluorite.

Physical properties Ophirite is an orange-brown, transparent mineral with a vitreous luster. It exhibits a hardness of 2 on the Mohs hardness scale. Ophirite occurs as tablet-shaped crystals on {001} with irregular {100} and {110} bounding forms. Ophirite has no observed cleavage and irregular/uneven fracture. The measured specific gravity is 4.060 g/cm3.

Optical properties Ophirirte is biaxial positive, which means it will refract light along two axes. The mineral is optically biaxial positive, 2Vmeas. 43(2)°. The refractive indices are: α ~ 1.730(3), β ~ 1.735(3), and γ ~ 1.770(3)°. Dispersion is strong, r > v. Its pleochroism is light orange brown for X and Y, and orange brown for Z, where X<Y<<Z. Observations indicate that chemical species are in their fully oxidized states.

Chemical properties Ophirite is a tungstate, and is the first mineral discovered containing [4]Fe3+[6]W6+9O34, a group in the structural unit of the ophirite polyanion. Tri-lacunary Keggin anions are well known in synthetic compounds, but ophirite is the first known example of a mineral with a tri-lacunary Keggin polyanion.The empirical chemical formula for ophirite calculated on the basis of 30 cations, is Ca1.73Mg3.99[Zn2.02Mn3+1.82(H2O)2(Fe3+2.34W17.99O68)2] · 45.95•H2O. The ideal formula for ophirite is Ca2Mg4[Zn2Mn3+2(H2O)2(Fe3+W9O34)2] · 46•H2O.

Chemical composition

X-ray crystallography A Rigaku R-Axis Rapid II curved imaging plate microdiffractometer using monochromatized MoKα radiation was used to collect X-ray diffraction data for ophirite. Ophirite is in the triclinic crystal system and in the space group P1. Its unit-cell dimensions were determined to be a = 11.9860(2) Å; b = 13.2073(2) Å; c = 17.689(1) Å; β= 85.364(6)°; α = 69.690(5)°; γ = 64.875(5)°; Z = 1.

Worked examples

Example 1 — a first encounter with Ophirite

Start with the simplest possible case. Write down what Ophirite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ophirite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ophirite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ophirite

In research: Ophirite appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ophirite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ophirite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Manganese minerals, Minerals in space group 1, Natural materials, so understanding it makes those chapters shorter.
In everyday life: Look for Ophirite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ophirite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ophirite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ophirite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ophirite in simple terms?

Why does Ophirite matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ophirite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ophirite.